The young mechanic had lost the sight in his right eye during the battle of Daraya. Still, he searched for his missing father for three days, combing destroyed buildings and piles of rubble. He finally found the old man dead on the outskirts of town, at a farm with three other bodies, boys aged 16-20. "Why kill an old man?" he asks.

He is not the only one to ask the question. An estimated 500 people were slaughtered in Daraya over two and a half days at the end of last month. Rebels and the government accuse each other. Left behind is a town destroyed beyond recognition.

According to Human Rights Watch (HRW), which has interviewed Daraya residents and analysed satellite images of the battle, evidence points towards government responsibility for the killings, although it is not clear whether uniformed men or the shabiha militia carried out the killings after the town was bombed by helicopters and shelled.

"What we don't know yet is who did the dirty work, the executions – whether it was men in uniform or shabiha," says HRW's Ole Solvang. "We're still investigating."

Witnesses speak of intense shelling from helicopters with mounted machine guns, mortars from a government military airport near the Mezzah neighbourhood, and snipers in buildings in the north of the city. They speak of bodies lying in the street, and groups of civilians hiding underground only to be found and summarily killed.

Shortly after the events, in an extraordinary act of indecency, the pro-regime television journalist Micheline Azar, entered the town to interview the dying, sticking her microphone in front of their bloody and wounded faces. She said the killings were "in the name of freedom". Not even children were spared her intrusions.

"It was horrific," says Reem, a Daraya resident. "She was a vulture. She went through the crowds talking to the wounded as though she was floating on water, as though there was not this scene of hell in front of her."

Ghost town

Two weeks on, Daraya still stinks of death. A poor Sunni suburb south of Damascus, it had been well known for furniture-making, and for its peaceful resistance before the conflict. Now it is a ghost town of shattered glass and broken graveyard walls, bombed vegetable shops and decapitated blocks of flats. Rank rubbish is piled on corners, uncollected. There is the unmistakable smell of rotting corpses that have not yet been removed from houses. A lone bicyclist makes his way awkwardly through the rubble and debris.

The town is still and lifeless. There is no way to confirm the death tally. It ranges from opposition reports of more than 1,000 to government figures of several hundred. The local gravedigger says he has already buried 1,000, and more bodies are found every day. The mounds of freshly dug, moist earth in the cemetery in the middle of town look like they harbour at least several hundred dead.

A woman who comes to the graveyard each day to check a list for news of her sons says: "We are still searching houses and abandoned ruins trying to find them." She says everyone waits for the hour when the gravedigger arrives and there are new bodies to identify.

In the ashen aftermath of war, it is impossible to imagine what this place looked like before, or what really happened here. It was first bombed, the centre flattened, before house-to-house operations were conducted. Some witnesses say men and boys were killed at close range with guns; others say knives were used.

"The problem is there is no food, no water, no electricity," says one family. Outside, two children play amid the rubble. "There's nothing to do, no one to play with," says six-year-old Rauda. "My friends left when the bombing started. I stayed close to my mother and held her. But she said we were not leaving."

Many fear becoming refugees as much as they fear the violence. "Would you leave your home?" asks Rashid, who owned a shop, now destroyed. "Would you take your life apart? We leave with our heads high, or we don't leave at all."

The attack on Daraya started on 20 August and intensified two days later. The Free Syrian Army withdrew from the town on 23 August and the army entered the next day. "The shelling started at 7.30am. There is no sound more frightening than rockets," says Rashid.

People hid in basements, and when the army arrived some were pulled out and killed outside; others were sprayed with machine-gun fire, Rashid says. "We had some informers who pointed out where opposition people were. They let the women run away but they shot the men one by one. In some cases, they went into the basement and killed old men and children – just because they were boys." His wife's four brothers and three nephews were among the victims.

Secret graves

A woman called Umm Hussein says she was rushing to escape the bombardment with her young daughter and 20-year-old son when a truck went by with soldiers shouting: "With our life, with our blood we will fight for Bashar." Umm Hussein and her children did not make it in time: they were stopped and, while she and her daughter were spared, her son was shot and his body taken out of town. There are rumours that some victims are being moved to secret graves, in an eerie reprise of Srebrenica.

But other people say the regime soldiers fed them and provided medical attention to the wounded. "They gave us bread," one man says. "Not all of them were monsters."

Will Daraya be a turning point in the conflict? Lakhdar Brahimi, the UN's special envoy, sent to the region after Kofi Annan's resignation, has said he is under no illusions about the difficulty he will face. Three months earlier the Houla massacre was also called a turning point.